Physical Activity Paradoxically Tied to Higher Coronary Calcium

Fran Lowry

September 23, 2021

Physical activity, long recommended by health experts to reduce risk for obesity, heart disease, type 2 diabetes, high blood pressure, hypercholesterolemia, and other cardiovascular disease risk factors, is also associated with increases in the amount of calcium deposited in the coronary arteries, new observational data suggest.

In a prospective cohort study of Korean men and women 18 years and older, participants who were the most physically active had the fastest progression of their coronary artery calcium (CAC) scores at 5 years, compared with those who were the least physically active.

Eliseo Guallar

"People who exercise may have an increase in their coronary calcium levels, but this is not necessarily bad news. This may mean that atherosclerotic lesions in the coronary arteries are becoming more stable and less dangerous, but we need additional research to understand these changes," Eliseo Guallar, MD, PhD, professor, Johns Hopkins Bloomberg School of Public Health, Baltimore, the study’s corresponding author, told | Medscape Cardiology.

This paradoxical effect notwithstanding, doctors should continue to advise their patients to follow the physical activity guidelines for Americans that were published in 2018, Guallar said.

"Physical activity is a key component of a healthy lifestyle. Our analysis can be useful, however, if someone starts exercising and sees that his or her coronary calcium score goes up," he said.

The study is published online September 20 in Heart.

The degree of build-up of calcium deposits in the coronary arteries is used to determine future cardiovascular disease risk and to guide treatment to prevent myocardial infarction and stroke. A CAC score of at least 100 Agatston units indicates that treatment with statins is warranted, the researchers write.

In the current study, investigators — led by Ki-Chul Sung, MD, Sungkyunkwan University School of Medicine, Seoul, Korea, and Yun Soo Hong, MD, Johns Hopkins Bloomberg School of Public Health — explored the link between different degrees of physical activity and the progression of CAC scores in healthy adults.

"While physical activity improves a wide array of cardiovascular and metabolic biomarkers, endurance athletes were more likely to have a coronary artery calcium (CAC) score >300 Agatston units or coronary plaques compared with sedentary men with a similar risk profile. It is not clear if exercise may itself be associated with calcification of the arteries," the authors write.

The researchers studied 25,485 participants (22,741 men and 2,744 women) who were part of the Kangbuk Samsung Health Study. All were free of cardiovascular disease at study entry and underwent comprehensive health screening exams at one of two major health centers in Seoul and Suwon, South Korea, between March 1, 2011, and December 31, 2017.

At each exam, participants filled out a questionnaire that included questions on medical and family history, smoking habits, alcohol intake, and education level.

Participants were also quizzed at baseline about their physical activity, using the Korean version of the International Physical Activity Questionnaire Short Form (IPAQ-SF).

On the basis of that, they were categorized into one of three categories: inactive; moderately active, defined as at least 3 days of vigorous-intensity activity for at least 20 min/day or at least 5 days of moderate-intensity activity or walking for at least 30 min/ day or at least 5 days of any combination of walking and moderate- or vigorous-intensity activities, attaining at least 600 MET-min/week; or health-enhancing physically active (HEPA), defined as at least 3 days of vigorous-intensity activity, attaining at least 1500 MET-min/week or 7 days of any combination of walking or moderate- or vigorous-intensity activities, attaining at least 3000 MET-min/week.  

Of the study participants, 47% were classified as inactive, 38% as moderately active, and 15% as HEPA.

Those who were more physically active tended to be older and less likely to smoke than less physically active participants. They also had lower total cholesterol, more hypertension, and existing evidence of calcium deposits in their coronary arteries.

A graded association between physical activity level and the prevalence and progression of coronary artery calcification was seen, irrespective of CAC scores at the start of monitoring.

At baseline, the estimated adjusted average baseline CAC scores in inactive participants was 9.45 (95% CI, 8.76 - 10.14), in moderately active participants was 10.20 (95% CI, 9.40 - 11.00), and in HEPA participants was 12.04 (95% CI, 10.81 - 13.26).

Compared with the least active participants, the estimated adjusted 5-year average increases in CAC was 3.20 (95% CI, 0.72 - 5.69) in moderately active participants and 8.16 (95% CI, 4.80 - 11.53) in HEPA participants.

A higher level of physical activity was associated with faster progression of CAC scores, both in participants with CAC score of 0 at baseline and in those with prevalent CAC.

The authors note there are several limitations to consider when interpreting their findings. These include the absence of an objective assessment of physical activity, the inability to evaluate the association between physical activity and CAC levels with incident cardiovascular events because of a lack of data, and the lack of information on incident myocardial infarction, stroke, CAC density, or volume.

Physical activity might increase coronary atherosclerosis through mechanical stress and vessel wall injury of coronary arteries; physiologic responses during exercise, such as increased blood pressure; increased parathyroid hormone levels; and changes in coronary hemodynamics and inflammation. "In addition, other factors, such as diet, vitamins, and minerals, may change with physical activity," the authors write.

"The second possibility is that physical activity may increase CAC scores without increasing cardiovascular disease risk," they write.

"The cardiovascular benefits of physical activity are unquestionable," the authors emphasize, adding that the national guidelines recommend at least 150 to 300 minutes per week of moderate-intensity or 75 to 150 minutes per week of vigorous-intensity aerobic physical activity.

"Patients and physicians, however, need to consider that engaging in physical activity may accelerate the progression of coronary calcium, possibly due to plaque healing, stabilization and calcification," they conclude.

Guallar added: "We would like to link our research to clinical outcomes, so that we can really be sure that the increase in coronary calcium scores does not imply an increase in risk."

"Do these findings mean that we should stop using coronary artery calcium scores to assess coronary artery disease?" ask Gaurav Gulsin, MD, and Alastair James Moss, MD, University of Leicester, United Kingdom, in an accompanying editorial.

The study highlights the complexity of interpreting CAC scores in patients who have implemented recommendations for physical activity or started statin therapy, they note.

"While proponents would argue that it is an effective tool to screen for subclinical atherosclerosis in asymptomatic individuals, clinicians should be cautious regarding the overuse of this test in otherwise healthy individuals. The coronary artery calcium paradox should not result in paradoxical care for our patients," Gulsin and Moss conclude.

Sung, Hong, and the other study authors report no relevant financial relationships. The British Heart Foundation provides funding support for Gulsin and Moss.

Heart. Published online September 20, 2021. Abstract, Editorial

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